The removal of H2S is involved in many occasions such as the deep processing and comprehensive utilization of coal, the exploitation of oil and gas, petroleum refining and petrochemical production. Currently, the industrial desulfurization method is divided into two kinds: dry desulfurization process and wet desulfurization process.
Dry desulfurization process and the regeneration method thereof employs solid adsorbent to remove the hydrogen sulfide and organic sulfur in the gas, which is simple and reliable in operation and has a relatively high degree of desulfurization. Dry desulfurization process is suitable for the treatment of a gas having low sulfur content, and is often used for fine desulfurization. Iron oxide is a commonly used desulfurizer for dry desulfurization process, while other kinds of desulfurizers, such as activated carbon, molecular sieve, manganese oxide, zinc oxide, etc., are seldom used due to high cost.
Wet desulfurization process and the regeneration method thereof can be divided into physical absorption method, chemical absorption method and oxidation reduction method according to the solution absorption and regeneration method. Wet desulfurization process has large treatment capacity and continuous operation, suitable for the situation where three are large quantity of gas to be treated with high hydrogen sulfide content. The physical absorption method is mainly the low-temperature methanol method developed by the Linde Group and Lurgi Corporation in the early 1950s, and this method has high gas purification degree, can allow selective absorption of CO2, H2S and separate removal and regeneration process thereof. However, the toxicity of methanol causes difficulties to the operation and maintenance. Chemical absorption methods mainly include monoethanolamine (MEA) method, N-methyldiethanolamine (MDEA) method and sulfone amine method, among which the monoethanolamine (MEA) method and MDEA desulfurization method are widely used in refinery gas and natural gas purification plant, and the sulfone amine method is mainly used for natural gas desulfurization industry, and is particularly effective for the removal of organic sulfides. Oxidation and reduction method is mainly used for the desulfurization of coke oven gas, and it mainly includes PDS method, tannin extract method, ADA method and modified ADA method. Oxidation and reduction method for desulfurization has low sour gas loading, large required solution circulation and high operation costs, and furthermore, the desulfurization waste liquid will produce secondary sewage and other problems.
In summary, among the existing desulfurization processes and regeneration methods, the amine method has annual desulfurization amount of more than 10,000 tons, and the dry desulfurization method has annual desulfurization amount of tens of tons to hundreds of tons commonly. For example, Chinese patent application document with a publication number of CN1307926A discloses a dry desulfurization process for flue gas using a circulating suspension bed and the regeneration method thereof, characterized by using a desulfurizer prepared by mixing dry lime, fly ash separated from a dust collector and water according to a certain proportion. The obtained desulfurizer has a certain activity and moisture content (8˜15%). The flue gas is injected into an absorption tower of the circulating suspension bed from the bottom thereof via a low resistance flue gas jet mechanism, and meanwhile atomized cooling water and the desulfurizer are separately sprayed into the lower part and the bottom of absorption tower of the circulating suspension bed. Most of the desulfurizer is circulated in the tower with an internal separation unit provided at the upper portion of the absorption tower of the suspension bed, and unreacted desulfurizer bed material leaving with the flue gas is separated through a gas-solid separation device provided outside the suspension bed and is sent back to the bed, thereby ensuring the utilization of the calcium-based desulfurizer. This method has overcome the drawbacks that the mortar pipeline are prone to fouling and clogging and flow resistance of flue gas is high and thus the costs is high for the system operation and maintenance when the lime slurry is directly used as the desulfurizer.
However, the “suspension bed” used in the above technique is actually a “fluidized bed”, wherein the solid desulfurizer is suspended in the flue gas flowing from bottom to up. It is well known that the distribution of solid particles in the bed is inhomogeneous in such a gas-solid fluidized bed, and the bed presents a two-phase structure, wherein one phase is a continuous phase with a relatively uniform distribution of particle concentration and porosity distribution close to the initial fluidized state, and the other phase is a discontinuous bubble phase that carries a small amount of particles moving upward through the bed. The excess amount of gas required for the initial fluidization gathers to form bubbles which moves upwards and gets ruptured on the bed surface to throw the particles to the space above the bed, which will result in large fluctuations of the bed interface and fluctuations of pressure drop. More unfavorably, the gas passing quickly through the bed in the form of bubbles has very little contact with the particles, while the gas in the continuous phase have a long contacting time with the particles due to the low velocity of gas, therefore resulting in nonuniform gas-solid contact, so the desulfurization efficiency of the above fluidized bed process can hardly meet the industrial requirements. Therefore, in view of small and medium-sized desulfurization projects, it is urgent to find a system for desulfurization and regeneration which have high desulfurization efficiency, simple operation, no secondary pollution, small occupation of land and low cost.